The Rf RWS fire curve is used in Netherlands for tunnel fire protection. It is based on the realistic tunnel fire caused by a tank truck in a tunnel which may lead to severe concrete spalling and consequently damage tunnel stability. The tunnel concrete lining therefore must be protected to ensure public mobility and safety. During the Rf RWS test, the fire curve reaches ca 1200° C. already in ca 5 min, then progressively increase to 1350° C. in 60 min, afterwards it slowly decreases to 1200° C. at 120 min. For immersed tunnels, the test criteria allow the maximum temperature (Tmax) at 380° C. on concrete surface, and only 250° C. at 25 mm inside the concrete surface. For drilled tunnels, the Tmax should not exceed 200-250° C. (cf. Both et al., TNO Centre for Fire Research, and Tan et al., Ministry of Public Works, The Netherlands). Today, this norm is also increasingly used in other countries as criteria for tunnel fire protections, such as, Belgium, Scandinavia countries, South Korea, and recently the USA. The Rf HCM condition is similar to the Rf RWS curve, applicable in France (FIG. 1).
Accordingly, the material used for tunnel fire protection must withstand the thermal shock, be resistant to abrasion necessary for tunnel cleaning, and insensitive to freeze/thaw attack. Preferably, it should be free of quartz and with low energy consumption for reasons of environmental protection and green footprint.
Only a few commercial sprays are available on the market capable of withstanding such Rf RWS condition. They are the CAFCO FENDOLITE MII of Promat, FireBarrier 135 of Thermal Ceramics and Meyco Fireshield 1350 of BASF.
EP 0 986 525 of MBT Holding discloses a spray composition comprising mainly a cementitious binder, a thermally treated shell sand and additives necessary for spray operation. The mortar is commercially available under the trade designation Meyco Fireshield 1350, with a cured density at ca 1500 kg/m3. The material can pass the Rf RWS test but at a thickness of 40 to 50 mm. The combination of high density and large thickness makes the spray operation difficult, especially when the spray has to cover complex profiles, such as steel frameworks.
EP 1 001 000 of Thermal Ceramics describes a spray which is claimed suitable for tunnels and it contains saw dust that releases smoke at high temperatures. This material has been on the market under the designation FireBarrier 135. It employs aluminate cement and kaolin, with a cured density of ca 1100 kg/m3, which is not only expensive, but also shrinks upon strong heating to such a degree that the product becomes cracked, a thick 38.5 mm has to be sprayed to survive the Rf RWS test, when tested by the TNO fire laboratory of Nederland.
Promat fire protection materials for tunnel fire protection are known on the market. EP 1 326 811 of Promat teaches a fire protection board in composition of aluminate cement, xonotlite, functional fillers and additives. It has excellent performance in Rf RWS condition, however it uses high aluminate cement as binder, the cost and energy consumption of raw materials are high. On the other hand, the CAFCO FENDOLITE® MII is a Promat spray fulfilling the Rf RWS condition. It comprises mainly of OPC and exfoliated vermiculite. This fire protection spray has been established worldwide, but supply of good vermiculite becomes increasingly difficult. Only a few vermiculite mines are known as asbestos free, their deposits are declining as result of industrial exploration, market prices are soaring.
CN 101863640 A provides an environment-friendly colored fire-proof coating for tunnels, comprising the following components in parts by mass: 10-50 parts of cement, 40-90 parts of expanded perlite, expanded vermiculite and precipitated calcium carbonate, 1-10 parts of inorganic mineral fibers, 5-30 parts of flame retardant systems, 0.1-5.0 parts of rubber powder, 0.5-3.0 parts of water reducing agents, air entraining agents and expanding agents and 0.5-2.0 parts of inorganic pigments.
The table below discloses the range described in the document. Taking the average of these ranges, the total amount is 123.5 parts which has been normalized to weight % in the last row of the table.
Average composition of CN101863640 (A)averageaverageCN101863640Arangetotalwt %cement 10-503024.3inorganic mineral fibre  1-1054.0perlite/vermiculite/PCC (CaCO3) 40-906552.6Al(OH)3/Mg(OH)2  5-3017.514.2gelling agent0.1-52.52.0air entrainer/foaming0.5-32.52.0agent/plasticizer0.5-2.010.8pigment
It follows that the amount of cement after normalization to 100 weight-% is in the range of 8 to 40 weight %. This material is intended to be stable up to 1100° C.